Connected: An Internet Encyclopedia
RFC 822 - 3.1.4. STRUCTURED FIELD BODIES

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### 3.1.4. STRUCTURED FIELD BODIES

To aid in the creation and reading of structured fields, the free insertion of linear-white-space (which permits folding by inclusion of CRLFs) is allowed between lexical tokens. Rather than obscuring the syntax specifications for these structured fields with explicit syntax for this linear-white-space, the existence of another "lexical" analyzer is assumed. This analyzer does not apply for unstructured field bodies that are simply strings of text, as described above. The analyzer provides an interpretation of the unfolded text composing the body of the field as a sequence of lexical symbols.

These symbols are:

- individual special characters
- quoted-strings
- domain-literals
- comments
- atoms

The first four of these symbols are self-delimiting. Atoms are not; they are delimited by the self-delimiting symbols and by linear-white-space. For the purposes of regenerating sequences of atoms and quoted-strings, exactly one SPACE is assumed to exist, and should be used, between them. (Also, in the "Clarifications" section on "White Space", below, note the rules about treatment of multiple contiguous LWSP-chars.)

So, for example, the folded body of an address field

                ":sysmail"@  Some-Group. Some-Org,
                Muhammed.(I am  the greatest) Ali @(the)Vegas.WBA

is analyzed into the following lexical symbols and types:

                        :sysmail              quoted string
                        @                     special
                        Some-Group            atom
                        .                     special
                        Some-Org              atom
                        ,                     special
                        Muhammed              atom
                        .                     special
                        (I am  the greatest)  comment
                        Ali                   atom
                        @                     atom
                        (the)                 comment
                        Vegas                 atom
                        .                     special
                        WBA                   atom

The canonical representations for the data in these addresses are the following strings:

                            ":sysmail"@Some-Group.Some-Org

and

                                Muhammed.Ali@Vegas.WBA

Note: For purposes of display, and when passing such structured information to other systems, such as mail protocol services, there must be NO linear-white-space between <word>s that are separated by period (".") or at-sign ("@") and exactly one SPACE between all other <word>s. Also, headers should be in a folded form.

Next: 3.2. HEADER FIELD DEFINITIONS

Connected: An Internet Encyclopedia
RFC 822 - 3.1.4. STRUCTURED FIELD BODIES